Faculty Publications
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Item Ubiquitous greenhouse monitoring system(Institute of Electrical and Electronics Engineers Inc., 2016) Rao, K.; Srijana, K.; Prasad, D.; Chandrasekaran, K.A greenhouse is a structure generally made of glass, designed to provide protection and controlled environment to raise plants indoors. In order to achieve high quality and quantity of produce, proper management and data collection of the greenhouse environment is required. Manual practice of plant monitoring is laborious and time consuming. The proposed greenhouse system is an application which demonstrates the concept of Internet of Things and involves ubiquitous monitoring and controlling of environmental parameters within the greenhouse, which directly or indirectly control the plant growth and so their production. The system thus designed, mainly aims to remotely monitor and control the greenhouse using temperature sensor, light sensor, soil moisture, water level sensor and actuators through a customized webpage. Moreover, real-time representation of the sensed data is graphically plotted as well as stored for improved monitoring and further analysis, illustrating the concept of cloud instrumentation. © 2015 IEEE.Item A comparison of power system signal detrending algorithms(Institute of Electrical and Electronics Engineers Inc., 2018) Rao, K.; Shubhanga, K.N.Wide Area Measurement Systems (WAMS) have facilitated tracking of oscillations in power system response signals. This has provided an impetus for application of signal measurement-based modal detection methods such as matrix pencil and Prony analysis. Detrending, which means removal of trend in a signal, is a pre-requisite for effective functioning of these modal detection methods. In this work, performance of three methods of detrending viz., Center-of-Inertia (COI)-based detrending, MATLAB function-based detrending and 'Zhou' detrending are compared with particular reference to power system signals. It is indicated that COI-based detrending is better suited to detection of modes from slip signals of generators. © 2017 IEEE.Item A Comparative Study between Prony and Eigensystem Realization Algorithm for Identification of Electromechanical Modes(Institute of Electrical and Electronics Engineers Inc., 2018) Sarkar, N.; Rao, K.; Shubhanga, K.N.Two measurement-based ring-down electromechanical mode identification algorithms, namely Prony and Eigensystem Realization Algorithm (ERA) are taken up for a comparative study. Since the number of excited modes might vary in a practical power system, it is not easy to determine the model order. This requires an iterative procedure in case of Prony whereas a Singular Value Decomposition (SVD)-based technique achieves this directly in case of ERA as demonstrated through two case studies. It is further shown that ERA estimates the signal better and generates less number of trivial modes as compared to Prony. © 2018 IEEE.Item Modal Analysis of Multi-machine Power System for Load Perturbation(Institute of Electrical and Electronics Engineers Inc., 2019) Zala, D.; Kn, S.; Rao, K.Load modeling has always been one of the important aspects of power system stability analysis. In this paper, efforts are made to study the modal behavior of multi-machine power systems for load perturbations. Provisions are made in the time-domain simulation environment to perturb different kind of load components by modeling them as ZIP loads. Resulting slip signals are subjected to Prony analysis to characterize the frequencies and damping of oscillations. Effects of continuous load variation on the power system stability is realized by performing random load perturbation in addition to sudden load changes. Further, an attempt is made to quantify the possible relation between the randomness of the continuous load change to the level of noise contamination in the slip signal of generators. Case studies are presented for 4-machine and 16-machine power systems. © 2019 IEEE.Item An Exposition of Digital Taylor-Fourier Transform(Springer Science and Business Media Deutschland GmbH, 2024) Rao, K.; Shubhanga, K.N.Digital Taylor-Fourier Transform (DTFT) is a Taylor series-based extension to Discrete Fourier Transform. It is becoming popular due to its ability to estimate off-nominal frequency phasors accurately, which is lacking in DFT, the conventional technique used in Phasor Measurement Units (PMUs). In light of this, a lucid presentation of the mathematical formulation of DTFT is considered instructive and hence the same is attempted here. Further, the ability of DTFT filter to accurately estimate off-nominal frequency phasors, off-nominal frequency harmonics and exponentially varying sinusoids is illustrated and reasoned out. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd 2024.Item On the Ability of Eigensystem Realization Algorithm to Identify the Dominant System Modes(Institute of Electrical and Electronics Engineers Inc., 2025) Rao, K.; Shubhanga, K.N.Eigensystem realization algorithm (ERA) is a popular ring-down mode identification algorithm used for power system identification from wide area measurement systems. This essentially involves construction of a state matrix from the measured ring-down response signal through some matrix manipulation. The eigenvalues of the state matrix thus obtained are known to match with the dominant system modes excited upon the occurrence of a disturbance. However, a mathematical proof for the similarity of the state matrix thus constructed from the response signal to the reduced-rank state matrix obtained through detailed modelling of the system is not available. This paper ventures successfully in this direction by relating the Vandermonde- and singular value-decompositions of the data matrix pertaining to pulse response. © 2025 IEEE.Item Fabrication and characterization of thermal evaporated n-Si/ p-ZnTe thin film heterojunction diodes(2013) Rao, K.; Bangera, K.V.; Shivakumar, G.K.The paper reports the fabrication and detailed electrical characterization of thermal evaporated n-Si/p-ZnTe thin film heterojunction diodes. The heterojunction diodes were prepared by depositing ZnTe films on n-Si substrates. The conduction mechanism, barrier height, space charge density and width of the depletion region were determined by I-V and C-V characteristics of the heterojunction diodes. The bandgap and activation energies of n-Si and p-ZnTe were also determined and a theoretical band diagram of n-Si/p-ZnTe heterojunction was drawn based on Anderson's model. © 2012 Elsevier B.V. All rights reserved.Item Influence of substrate temperature and post deposition annealing on the properties of vacuum deposited ZnSe thin films(2013) Rao, K.; Bangera, K.V.; Shivakumar, G.K.The effects of substrate temperature and post deposition annealing on the structural, optical and electrical properties of vacuum deposited ZnSe thin films are presented here. The chemical composition of the films varied drastically with substrate temperature which in turn caused changes in various properties of the films. The grain size of the films increased with substrate temperature and also after annealing. The electrical properties of the films were found to be varying as a function of chemical composition and grain size. © 2012 Elsevier Ltd.Item MAPE-An Alternative Fitness Metric for Prony Analysis of Power System Signals(De Gruyter peter.golla@degruyter.com, 2018) Rao, K.; Shubhanga, K.N.Phasor Measurement Units have facilitated tracking of oscillations in power system response signals. This has provided an impetus for identifying unstable component modes directly from oscillatory signals. Prony analysis, the earliest method proposed for this purpose, throws up some trivial modes. These not only distract the analyzer but also prolong processing time thereby delaying corrective action. Hence the fitness metric chosen should serve to minimize the number of trivial modes. The conventional fitness metric is Signal-To-Noise Ratio (SNR), which is actually Signal-To-Estimation error Ratio (SER). This paper proposes that Mean Absolute Percentage Error (MAPE) can also serve well as a fitness metric. It is shown through case studies carried out on well-known four-machine power system that there are a few cases where MAPE performs better than SER while in some instances SER works better. This inference is verified even in the presence of measurement noise. Hence a novel fitness metric is proposed combining MAPE with SER. Case studies on simulated signals obtained from New England-power system prove that this novel metric can achieve considerable reduction in processing time. Besides, an exponential binary search has been suggested for determining the optimal model order in minimum number of iterations. © 2018 Walter de Gruyter GmbH, Berlin/Boston 2018.Item Equivalence of Matrix Pencil and HTLS Ring-Down Electromechanical Mode Identification Algorithms(Institute of Electrical and Electronics Engineers Inc., 2023) Rao, K.; Shubhanga, K.N.Matrix pencil and Hankel total least squares (HTLS) are two popular ring-down electro- mechanical mode identification algorithms. The appeal of these algorithms can be attributed to faster execution due to the non-iterative procedure of model order determination based on singular value decomposition of the data matrix. In this paper, these two algorithms are shown to be equivalent - the data matrix in one being the transpose of that in the other. Although this equivalence is proved in the context of power systems, it is valid for other areas of system identification as well. Further, the performance of these algorithms is examined as noise level in the signal increases, and it is shown that these work right down to an SNR of 1 dB provided the signal has only poorly damped modes. © 2013 IEEE.